The strongest open-source alternatives to Phoenix for building AI agents — observability ranked by GitHub traction, each with a head-to-head.
Phoenix (★ 10k) is Arize's open-source observability for LLM apps — OpenTelemetry-based tracing and evaluation. If it is not the right fit, these 2 observability cover the same ground — Langfuse is the most-starred option below. Or browse the best observability and Phoenix's own page.
Open-source LLM engineering platform — tracing, evals, prompt management, and metrics for agent apps. Best for LLM tracing.
Open-source observability for LLM apps via a proxy — logging, caching, and cost tracking with one header. Best for cost tracking.
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